Sample for Map<String, String> to OptionSet.

Please ignore the import changes.

This is one way to provide a Map interface to parsed options.  I wanted some flexibility in how map key are chosen.  For example in my use case I want to map options onto properties to aid applications in having command line overrides for configuration.

One variant is to prefix the keys so you can have more complex properties than just "debug", e.g., the "--debug" flag becomes the "my.app.debug" key which aligns with a properties file entry somewhere.